Is it a pulled muscle or sciatica?

Relatively healthy 32f, overweight (weight loss in progress) and never really suffered any back pain. Christmas Day morning I was on my feet in the living room and reached for a present. Queue a lightning bolt sensation in my lower back that almost took me off my feet. Ever since my lower back has been very stiff, especially when seated. No pain radiating down my legs. Other than an ache in my thigh. It seems to mostly hurt on my right side. I’m a little bit of a hypochondriac so I’m already thinking the worst. Ice is helping and I’m taking anti inflammatories but the pain is still there. I almost had another flare up last night because of an uncomfortable sitting position but narrowly avoided. Now I’m scared to death of moving for fear of the pain again. I have a GP appt in two weeks (joys of UK NHS waiting times) but I’ve made an appointment with a private chiropractor for next week too. Does anyone have any advice/words of wisdom? Sincerely, a girl wanting to rip her own muscles/nerves/tendons out of her back.